Improvement in cams for operating valves for steam-engines



4 E. SPRAGUE. Cams for Operating Valves for Steam-En ines; N0, 134,944l Pmmed1an.14,1873.

mamar @egim NITED STATES ATENT FFICJEn EDWIN SPR-AGUE, OF ALLEGHENY, PENNSYLVANIA.

Specification forming part of Letters Patent No. 134,944, dated January 14, 1873.

To all whom it may concern:

Be it known that 1, EDWIN SPRAGUE, of the city and county of Allegheny and State of Pennsylvania, have invented a new and useful Improvement in Method of Tripping Out-Off Gear for Steam-Engines; and I do hereby declare that the following is a full, clear, and exact description thereof, reference being had to the accompanying drawing and to the letters of reference marked thereon.

In the construction of that class of steamengines provided with what is known as cutoff valve-gear, a number of cams, cam-rods, rock-shafts, and other mechanism are necessary to the proper workin g of the valves used for supplying the cylinder with steam, and for exhausting it from the cylinder, and this complication of mechanical devices for operating the valves, so as to cut-off the supply of steam to the cylinder and exhaust it at the proper time, has caused great complication in the construction of such steam-engines, making them costly and very liable to become impaired and inoperative.

The skillful engineer has long been aware that if a continuous motion of the cam-rod could be obtained7 then the operating mechanism for working cut-off and full-stroke valves could be greatly simplified, and the cost of such engines very much diminished. N ow, the object of my invention is to obtain a continuous motion of the cam-rod through the medium of a single full-stroke cam, thereby avoiding the use of a number of cams, ca1n-rods,rockshafts, Src., for operating cutoff valves in steam-engines. The nature of my invention consists in arranging the ordinary axis of motion of the common full-stroke cam eccentric to the axis ofthe crank-shaft of the steam-engine so that it will be rotated around the axis of the crank-shaft, thereby imparting to the cam-rod and its yoke a continuous motion.

To enable others skilled in the art to make and use my invention, I will proceed to describe its construction and operation.

In the accompanying drawing7 which forms part of my specication, Figure l is a side view of my improvement in cams, and also represents its yoke. Fig. 2 is a face view of the cam.

In the accompanying drawing, A represents the cam-yoke, which moves in slides or guides D; the cam-rod may be attached to the yoke at either of the points x. B represents an ordinary full-stroke cam, and the point marked e represents its ordinary axis of motion, and the point marked f represents the axis of motion ofthe crank-shaft C. The novelty of my invention consists in securing the cam B on the crank-shaft C, so that its ordinary axis of motion, which is at the point e, will be rotated around the axis of motion of the crankshaft G, which is at the point marked f, whereby the distance from the point gl of the cam B to the point f will be greater than the distance from the point f to thel points h and z' of the cam. The point 'i of the cam B would, if ro` tated on its ordinary axis e, impart the greatest movement to yoke A and cam-rod attached toit; but by having the axis of the cam at the point f the motion of the yoke A will be continued until the point g has reached the line J of the yoke, at which point the cam will commence moving the yoke back. By thus arranging the cam on the crank-shaft C, as hereinbefore described, a continuous motion is imparted to the cam-yoke and the rod attached to it, so that after the cam-rod has moved the operating-gear used for the purpose of lifting the supply and exhaust valves it will continue its motion until the operatinggear of the valves has allowed them to drop, and thereby close the steam-ports of the cylinder.

Having thus described the nature, construction, and ope-ration of my improvement, what4 I claim as of my invention is- The hereinbefore-described method. of tripping cut-off gear77 of steam-engines by the ordinary full-stroke cam, so that its axis of motion shall be eccentric to its ordinary axis of motion, whereby it will perform the function of the full-stroke cam, and also trip said cutoff gear by a single cam-rod and cam-yoke, as and in the manner set forth.

EDWIN SPRAGUE.

Witnesses:

A. C. J oHNsroN, JAMES J. JoHNsroN. 

